Similar to a stye except can get really large and may need surgical excising. My 2.4 ds has had a few days of conjunctivitus over xmas, then a stye that has kept coming and going, and now apparently a (so far) small red slightly swollen patch on his eyelid which the locum doctor diagnosed as the above. (I say diagnosed, he looked it up in a med dictionary and then held it out for me to read!!!)
All he said was 'let's not take any chances' and referred us to an opthamologist. Came home and googled it and everything I have read seems to indicate that in the early stages it can be treated with a/biotic eye drops etc. Am seeing my own gp in about 10 days when he returns from holiday, but was wondering if anyone could put my mind at rest in the meantime?